package 练习;

public class circle {
    double r;
    public void area(){
    double pai = 3.14;
    double s = pai * r * r;

        System.out.println("面积为:" + s);
}

public void area2(double pai){

    double s = pai * r * r;

    System.out.println("面积为:" + s);
}

//传递一个 半径 和 pai 给我返回面积
public double area3(double r,double pai){

    double s = pai * r * r;

    return s;
}


}
